In the meat industry it is becoming increasingly important for meat products to be accurately described to ensure that the correct products are directed to specific markets, maximum returns are gained for the different products and products can be changed over time to suit the requirements of the market. This is particularly so in the meat processing section of the industry which operates between the producers (farmers) and wholesale or retail consumers who purchase either whole carcases or boned-out cuts of meat in cartons. The requirements of the consumers (in various markets such as Australia, Japan, USA, Korea, EEC etc) are varied, with the potential for both large premiums and also heavy discounts for providing either the correct or wrong products respectively.
In the USA and Japan, for example, centrally controlled grading schemes have evolved to cater for this requirement by inspecting the carcases in the abattoir and assigning an overall grade to the meat products in the carcase which is based on several individual characteristics. The grading is based on an expert assessment of a cross section cut through the carcase at a specified site, usually between two particular ribs. This cut exposes several muscles, in particular the longissimus dorsi or ribeye muscle which is one of the more valuable portions of meat in the carcase, as well as intermuscular fat deposits, a cross section of the subcutaneous fat layer and any bones/ribs that may be present. Both US and Japanese grading schemes attach great significance in the grading schemes to the level of intramuscular fat contained within the ribeye (marbling), the colour of the ribeye muscle, the area of the ribeye and the colour of the intermuscular fat surrounding the muscles. These are all important quality measures although the ribeye area, intermuscular fat and subcutaneous fat thickness can also be used as a quantitative measure of the carcase by predicting the relative amount of meat in the whole carcase (i.e., lean meat yield %). In the US system the carcase is assigned a marbling category (slight, abundant, etc) based on comparison to a set of photographs published by the US Department of Agriculture (USDA), who are also responsible for training all graders within the industry. Meat colour is judged by reference to a few descriptive terms (bright cherry red, etc) and similarly for fat. Ribeye area is estimated in square inches but is mainly used to assign a yield grade rather than quality grade. Along with other characteristics (age, etc) these descriptions are used to assign the carcase/meat into a few overall grades ie premium, choice, select, etc.
The Japanese grading system, for example, goes a stage further by having a reference set of artificially made `chips` which are used for comparative scoring of meat colour, fat colour and marbling. Thus, an individual carcase can be given a score of marbling (1-12, indicating no fat to abundant fat) meat colour (1-9, indicating light to dark) and fat colour (0-9, indicating white to dark/yellow) where the marbling score in particular has a great bearing on the value assigned to the meat.
In Australia, AUSMEAT have developed a Chiller Assessment Method which is similar to US and Japanese methods. Usually, the assessor is also trained to make objective measurements of subcutaneous fat depth at a particular site with a ruler, and ribeye area using either a grid and manual counting technique or a digitising tablet which computes the area from an outline traced around the ribeye boundary with a stylus.
A typical abattoir processing &gt;500 carcases per day would need to train several skilled, senior personnel to be qualified chiller assessors to cope with assessing every carcase. These assessors would typically be required to start early (ie be paid penalty rates), would require expensive, ongoing training and be subject to variability between their assessments.
Papers have been published by Chen and McDonald (Chen and McDonald, Proc. 1989 ASAEICSAE meeting. & Chen and McDonald, Trans ASAE, 33 [6], November 1990.) These papers describe techniques for the identification of the ribeye muscle from among the image of the total cross section and also for the measurement of the marbling score on a given ribeye muscle. The papers do not describe a hardware system in any detail but concentrate on the software/signal processing methods for performing the image analysis. It appears that all development work was based on photographs taken of quartered carcases for the ribeye descrimination work and 6 USDA marbling standard photographs for the marbling work. The whole technique as disclosed is based on the use of monochrome images.
A prior art technique for delineating the ribeye muscle is based on `morphological operations` to separate muscles which are directly adjacent to the ribeye muscle.
A prior art discrimination technique essentially revolves around a `fixed gray level thresholding` method, with some pre-processing to remove large scale variations due to lighting variation across the sample/image.
Earlier patents have also tried to make use of automated methods for evaluating the quantitative and qualitative characteristics of the rib section. Examples are provided in U.S. Pat. Nos. 3,154,625 (Oct. 1964), 4,226,540 (Oct. 1980), 4,413,279 (Nov. 1983).
U.S. Pat. No. 4,226,540 discloses the use of a video cambera but uses only very basic methods for attempting to quantify the relative amounts of fat and meat in the sample.
Another field of use of an image analysis system is in assessment of retail cuts of meat. For example, a purchaser of large quantities of meat cuts, e.g. a catering establishment supplying a hospital or airline, needs to monitor the quality of meat cuts being supplied and such monitoring needs to be as consistent and objective as possible. Similar parameters to carcase assessment parameters need to be measured, although other meat sections may be involved, e.g. tenderloin, striploin, tenderloin centre cut, etc.
Assessment of other objects may also usefully employ an automated image analysis system, e.g. assessment of fish, fruit, manufactured food products, or other natural or manufactured articles.